The present invention is in the field of methods and devices for assembling multi-layered electrical junction boxes, especially those used in automotive applications.
Automotive junction boxes, power distribution centers, and the like typically comprise stacked array of plastic insulating plates and covers, which are sandwiched and at least semi-permanently secured together prior to being installed in a vehicle. Referring to FIG. 1, an exemplary representation of a prior art junction box 10 includes a plastic bottom cover 10a, a plastic top cover 10b, and a plurality of insulation plates 10c sandwiched therebetween in stacked relationship. Insulation plates 10c are provided with various conductive pathways typically formed with metal bus bars laid out in circuitous arrangements designed to inter-connect and re-route multi-branch wiring from vehicle electrical systems using various electrical components (fuses, relays, etc.) plugged into the junction box via suitable receptacles formed in top cover 10b. 
As vehicles incorporate ever greater numbers of electrical components and systems, junction boxes are increasingly designed to accommodate ever greater numbers of electrical components. At the same time, junction boxes are expected to remain the same size, or to be made smaller.
A typical method for assembling junction boxes such as that shown in FIG. 1 is illustrated in FIGS. 2A-2G. The junction box covers 10a, 10b and insulation plates 10c are each provided with aligned, coaxially mating pilot holes 12, 14, 16 sized to receive an alignment pin or pilot 18 at an assembly station 19. As best shown in FIGS. 2A-2D, bottom cover 10a, insulation plates 10c, and top cover 10b are sequentially lowered onto stationary pilots 18, the pilots engaging and passing through the respective holes, 12, 14, 16 to register and maintain the stacked plates and covers in proper alignment until the stacked components can be at least semi-permanently secured together. For this purpose, the assembly station will typically have at least two pilot pins 18 to prevent rotation of the stacked, registered junction box components, although it may be possible in certain cases to use a single, asymmetrical pilot engaging asymmetrical pilot holes in the stacked components to prevent rotation.
Referring to FIG. 1 again, lower cover 10a is provided with weld boss, heat stake or similar structure generally in the form of upright pin members 20 designed to pass through mating stake holes 22 and 24 in the top cover and insulation plates as the covers and plates are being aligned and registered on pilot pin 18 at the assembly station. As shown in FIGS. 2E-2G, the insulation plates and top cover are lowered down over heat stake pins 20 and the upper ends of the heat stake pins protruding through holes 22 in the top cover are then flattened or otherwise deformed in known manner using a technique such as heat staking, sonic welding, and others known to those skilled in the art. This locks the assembly of stacked junction box components together and the junction box is then removed from pilot pins 18 at the assembly station for installation in a vehicle.
A significant drawback of the foregoing method for aligning and staking junction box components lies in the fact that valuable junction box layout and component receptacle space is taken up by the pilot holes and stake holes. The placement of the pilot and stake holes complicates the routing of bus bars on the insulation plates and must be factored into the placement of plug-in components on the top cover, an increasingly complicated procedure.
The present invention eliminates the need for separate pilot and stake hole structure by replacing the usual pilot pin at the assembly station with a plastic heat stake pin or weld boss designed to fit through the pilot holes formed in the junction box components and to be melted or otherwise deformed in the manner of a conventional heat stake. In a preferred form, this combination pilot pin/heat stake is configured as the usual pilot pin, is held at an assembly station as if it were a pilot pin, and the pilot holes on the junction box components are stacked in place over the pilot pin/heat stake for proper alignment and registration. Immediately thereafter, and without removing the registered components from the station, the upper end of the pilot pin/heat stake is melted, punched, or otherwise deformed in the manner of a typical heat stake to lock the stacked components together.
In a most preferred form of the invention, the pilot pin/heat stake (hereafter xe2x80x9cpilot stakexe2x80x9d) has a lower plug portion adapted to be securely but removably seated in a holder or jig at the assembly station. The jig securely positions the pilot stake in an upright position ready to receive the junction box components in stacked relationship thereover. The jig also provides a secure base or anvil for the bottom of the pilot stake while the upper end of the pilot stake is being deformed to lock the stacked junction box components togther. Once the deformation has taken place, the pilot stake (which is now locked to the junction box) can be pulled free from the jig.
In yet a further preferred form of the invention, the configuration of the jig for the pilot stake combines with the configuration of the pilot stake when the pilot stake is seated therein to replicate the configuration of the original pilot pin for which the pilot holes in the stacked junction box components were designed. The assembly can thus be considered a composite pilot pin with a breakaway heat stake feature.